1. Field of the Invention
The present invention relates to configuration management or control processing for a computer system, and more particularly to configuration management or control processing for a computer system utilizing remote copy and having a plurality of storage systems.
2. Description of the Related Art
Data storage markets have a need for a so-called disaster recovery system which prevents a data loss even if a storage system storing a huge amount of data is destructed by disaster or the like. In order to satisfy this market need, a computer system has been provided which backs up data by utilizing remote copy technology. With this technology, the same data is stored in storage systems installed at two locations sufficiently remote from each other. As data in one storage system is updated, this update is reflected upon the other storage system by remote copy. Integrity of data in two storage systems can therefore be ensured.
JP-A-2003-122509 discloses a computer system which installs storage systems at three locations sufficiently remote from one another, in order to improve security of data. Data integrity between a first storage system used by ordinary business and a remote second storage system is retained by synchronous remote copy. Data integrity between the first storage system and a remote third storage system is retained by asynchronous remote copy.
When the first storage system becomes unable to use for business because of failure to be caused by disaster or the like, the second storage system inherits the business of the first storage system. In this case, if the second storage system cannot be used either, the third storage system inherits the business of the first storage system.
According to JP-A-2003-122509, before the second storage system inherited the business of the first storage system starts operating, data integrity between the second and third storage systems is retained. After the second storage system starts operating, update of data in the second storage system is reflected upon the third storage system by remote copy. Therefore, when a failure occurs in the second storage system, the third storage system can inherit the business of the second storage system.
A data update method of JP-A-2005-84953 discloses means for shortening the time taken to retain data integrity between the second and third storage systems. According to this technique, when data integrity between the second and third storage systems is to be retained, difference data in one storage system is reflected upon the other storage system, to thereby reduce a copy capacity of data and thus realize a time reduction. In this specification, data integrity retention technique disclosed in JP-A-2005-84953 is called “delta-resync”.
As disclosed in JP-A-2005-84953, however, various processings different from conventional remote copy are required in order to perform delta-resync, such as check processings including acquisition of a journal logical volume, storage of change information in the journal logical volume, comparison of change information during delta-resync.
Furthermore, if it is judged that delta-resync is impossible, during check processings after the first storage system is destructed by disaster or the like, all data is copied, posing again the issue solved by JP-A-2005-84953. Namely, long time data copy causes the second storage system impossible to be used for business.